Piston Dishing Questions and gasket suprise

[bratcop]

So the build is coming along. I received all my parts from EngineTech today...and they are pretty and shiny....but seriously,

The pistons I ordered from engineTech are unbranded Silvolite 3241HC (according to the cast numbers inside.) I want to dish them to get my quench down between .040 and .050, but keep my compression around 9.5:1. If I deck to .008" piston to deck clearance, use the head gasket, compressed to .038, and dish the pistons from 14.1 to 20 cc, I get scr of 9.6:1 with .046 quench (which I will tolerate, but would like tighter quench). What I need to know, is can these pistons be dished safely to this volume? What is the minimum thickness I should seek to exceed or meet when dishing a piston? I just want other's opinions to check against what my machine shop tells me.

Also, when I opened up my gasket kits from EngineTech today, I found a Victor head gasket, MLS style (Multi-Layer Steel) which when mic'd gave a thickness at .038 thickness. I am assuming this is the Victor gasket that everyone is looking for? Just so you know, it is what EngineTech included in my upper gasket set for an '01 4.0l...

When dishing the pistons, I would like to maintain the dish contour they already have, rather than dish out the entire top, as this would maintain optimum quench surfaces, everyone agree?

Who is the piston expert here, oleshot? Please chime in...

Bratcop

[John]

"When dishing the pistons, I would like to maintain the dish contour they already have, rather than dish out the entire top, as this would maintain optimum quench surfaces, everyone agree?"
It is not necessary to maintain stock contour, but most seem to do so. I have ran a lot of dish shapes and some domes in different builds. There is photos posted on this board of pistons nicely fully dished spherically. They work well.

By the way several of the manufactures consider .3" as min thickness for the tops.
John

[Alex22]

Whats the part number on that head gasket? I'm looking to get the thinnest one I can for my build (whenever I get my ass in gear and build this thing)

~Alex

[SilverXJ]

The Victor gasket is not a MLS, do I don't think that is what you have. Its also pretty thin. Are you sure its .038? That is even thinner than the Victor one.

[bratcop]

It's definately a Victor gasket, part number on it was followed by a v with a circle around it and it definately is a MLS gasket, three layers. My machinist and I mic'd it in about 5 different places with the thickest being .039, everything else was .038. We did not mic it where the layers were affixed with (adhesive or whatever you would call it) because he said that would all get compressed to the thickness of the three sheets anyway...I will have to get back to the shop to give you a number....I am guessing that it might not compress all the way to a .038 in those areas, but he thinks it will.

[oletshot]

I'm definitely not an expert. Others have told me I do a nice job machining them, but thickness advice I try to avoid. I will tell you what I have heard from others, who probably aren't experts either.

1. I've heard Silvolite 2228 & 2229 are the only pistons that are thick enough to machine. Although,I found my stock pistons to be thicker than the Silvolites and machined them.
2. One of my customers told me that Silvolite told him .190" a minimum thickness for the 2229s.
3. Some people claim to have dished the 2229s down to 30cc's and have had no problems with them. I haven't modeled 30cc's in CAD yet but that's got to be really close to the .190" mentioned above.
4. I've machined Speed Pro hyper pistons for Mgardiner1 (I don't recall the part# on these off hand, I think they were HC821CP). I was able to get them to 20cc's and still have about .205" thickness. These are in his stroker, but he just got it on the road the other day (literally if you check his "Look what happened to me today!! " post).

Do you have a way to measure the thickness from the top of the piston to the bottom of the dish inside the piston?
For my info, what did your machine shop recommend?

[SilverXJ]

2. One of my customers told me that Silvolite told him .190" a minimum thickness for the 2229s.

I can confirm that as that is what I was told when talking to Silvolite/Keith Black.

The minimum thickness is .190" and the hyper material is very hard, use carbide or diamond cutters.

[bratcop]

Well, I just send Silvolite this exact question, and I will post the response I get, so that we can all know the answer.

Additonally, I will get the gasket number tomorrow from my head gasket, as well as take some pics of my gasket to post, so you can all see what I am talking about. Thanks for all the input so-far.

Oletshot, thanks for the info on the pistons, and I must agree, you do some nice work. If my machinist can't do the machining, I might be sending them down to you. What is your turn around time on something like that? I just live up the coast from you, maybe the wife and I could make a weekend of it in Shy-town sometime and personally deliver them if necessary. Thanks again.

Bratcop

[Mgardiner1]

Oletshot had my pistons back to me in just over a week. The only reason for the delay was him being busy with work and his own life. No complaints here on the turn around time.

The pistons he dished for me were H802CP's, .060 over. I confirmed his calculations and cc'd them with water. The were indeed every bit of 20cc's.

[seanyb505]

Im running the dished 2229s to 30cc with no problems related to pistons as of yet.

[bratcop]

Does anyone know if the 2229 and 3241hc's have the same thickness on the piston top? I understand that the 2229 can be dished to 30cc, but is that related in any way to what my 3241HC can be safely dished to? I am not being sarcastic here, just wondering if I am ignorant to the fact that they are from the same factory casting or something similiar...

Bratcop

[bratcop]

So here is what I got back from Silvolite Tech email when I asked them about dishing my pistons...

"Hi
Stock cast pistons are not designed to be altered, minimum thickness would be aproxamately .200". I would recomend premium fuel and a better unaltered piston fot that high of compression unless you stay above 6000 feet above sea level.

A better idea would be to use a forged piston and a long rod, see http://www.kb-silvolite.com/forged.php? ... s&P_id=543
Bob Borowick
tech dept
800-648-7997 ext 187


I had told him I hoped to run at around 9.6:1 SCR and wanted to use 87 octane gas. Apparently he thought not. I assume that the first line, about not altering pistons is required by him for liability reasons? Or am I nuts for considering dishing these because they are Hypereutectic? Isn't Hypereutectic harder than cast aluminum, and therefore stronger at thinner thicknesses?

regarding my head gasket, the Victor number is 54249S, and here are some pictures....for the measurement of .038/.039 we did not measure at the blue part, just the thickness of the 3 metal layers compressed only by the mic.

Overall Gasket Shot

IMG_0095.JPG

part Number shot

IMG_0097.JPG

Also here is a shot of my machined throttle body where we removed the "choker" at the bottom...

IMG_0099.JPG

Also measured the thickness of the piston head, at the thinnest area in the dish it is .250".....
Should that leave me enought to dish to 21cc?

Thanks...
Bratcop

[oletshot]

That tells me you can remove about .050" from the the factory dish which is supposed to be 14.1 cc's. Trouble is, the actual factory dish isn't always what the catalog says. I'll try working it up on my old laptop here, but it's very slow. If I get PO'd at the laptop, I'll do it tomorrow at work and give you a ballpark answer. If you could give a dimension from the top of the piston to the bottom of the dish on the inside of the piston, I could give a more acurate answer. If you have calipers, you could measure from the top of the piston to the bottom of the skirt (overall height) and subtract the bottom of the skirt to the bottom of the dish inside the piston (inside height). Overall minus inside equals thickness from top to inside surface. I think that makes sense. Otherwise just measure depth of factory dish and add the .250".

[oletshot]

What I came up with was this, 14.1cc's should be about .115" deep dish. I can take the dish down another .050" making the dish about .165" deep which would leave the thickness at .200". This gives you 20cc's of dish. It seems the silvolite 3241's are very similiar to the speed pro 802's. Of course this assumes that your piston's dish is actually .115" deep.

Seanyb505, did you keep the dish close to the factory shape or did you have to lose the quench area on the 30cc 2229s?

[seanyb505]

I bought them from another guy having alreayd been dished. They retained the quench plain.

viewtopic.php?f=8&t=71&start=0

Sixth picture down.